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| 型号： | MAX5022EUT+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 7/11页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR FLYBK ISO SOT23-6 |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 290kHz |
| 占空比： | 76% |
| 电源电压： | 11 V ~ 28 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | SOT-6 |
| 包装： | 带卷 (TR) |
Current-Mode PWM Controllers for Isolated
Power Supplies
85VAC (corresponding to 120VDC) to the 24V wakeup
level results in a resistor value of about 1M ? . If we
assume R S values between 750k ? and 1M ? , then at
the high-line voltage of 265VAC (corresponding to
374VDC) power dissipation will be between 140mW to
190mW. A single 1/4W resistor or a series combination
of two 1/4W resistors is adequate.
Undervoltage Lockout (UVLO)
The device will attempt to start when V IN exceeds the
UVLO threshold of 24V. During startup, the UVLO cir-
cuit keeps the CPWM comparator, ILIM comparator,
oscillator, and output driver shut down to reduce cur-
Optocoupler Feedback
The MAX5021/MAX5022 do not include an internal error
amplifier and are recommended for use in optocoupler
feedback power supplies. Isolated voltage feedback is
achieved by using an optocoupler and a shunt regula-
tor as shown in the Typical Operating Circuit . The out-
put voltage set point accuracy is a function of the
accuracy of the shunt regulator and resistor divider.
When a TLV431 shunt regulator is used for output volt-
age regulation, the output voltage is set by the ratio of
R4 and R5 (Figure 1). Output voltage is given by the
following equation:
V OUT = V REF × ? 1 +
?
rent consumption (Functional Diagram) . Once V IN
reaches 24V, the UVLO circuit turns on both the CPWM
and ILIM comparators, as well as the oscillator, and
allows the output driver to switch. If V IN drops below
?
?
R 4 ?
R 5 ?
R CS = CS
10V, the UVLO circuit will shut down the CPWM com-
parator, ILIM comparator, oscillator, and output driver
returning the MAX5021/MAX5022 to the startup mode.
N-Channel MOSFET Switch Driver
The NDRV pin drives an external N-channel MOSFET.
The NDRV output is supplied by the internal regulator
(V CC ), which is internally set to approximately 9V. For
the universal input voltage range, the MOSFET used
must be able to withstand the DC level of the high-line
input voltage plus the reflected voltage at the primary
of the transformer. For most applications that use the
discontinuous flyback topology, this requires a MOS-
FET rated at 600V. NDRV can source/sink 150mA/
250mA peak current, thus select a MOSFET that will
yield acceptable conduction and switching losses.
Internal Oscillator
The internal oscillator switches at 1.048MHz and is
divided down to 262kHz by two D flip-flops. The
MAX5021 inverts the Q output of the last D flip-flop to
provide a duty cycle of 50% (Figure 3). The MAX5022
performs a logic NAND operation on the Q outputs of
both D flip-flops to provide a duty cycle of 75%.
where V REF = 1.24V for the TLV431.
During normal operation, the optocoupler feedback pin
(OPTO) is pulled up through a 6.2k ? resistor to the
internal supply voltage of 5.25V. When the device is in
UVLO, OPTO is disconnected from the 5.25V regulator
and connected to ground (Functional Diagram). This
helps initial startup by reducing the current consump-
tion of the device.
Current Limit
The current limit is set by a current sense resistor, R CS ,
connected between the source of the MOSFET and
ground. The CS input has a voltage trip level (V CS ) of
600mV. Use the following equation to calculate the
value of R CS :
V
I PRI
where I PRI is the peak current in the primary that flows
through the MOSFET. When the voltage produced by
this current through the current sense resistor exceeds
the current-limit comparator threshold, the MOSFET dri-
ver (NDRV) will quickly terminate the current ON-cycle,
typically within 60ns. In most cases a small RC filter will
be required to filter out the leading-edge spike on the
sense waveform. Set the corner frequency at a
OSCILLATOR
1.048MHz
D
Q
Q
D
Q
Q
262kHz WITH 50%
(MAX5021)
262kHz WITH 75%
(MAX5022)
few MHz.
Applications Information
Universal Off-Line Power Supply
Figure 1 shows the design of a 5V/1A isolated power
Figure 3. Internal Oscillator
supply capable of operating from a line voltage of
85VAC to 265VAC. This circuit is implemented in the
MAX5022EVKIT.
_______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX5022EVKIT | 功能描述:电源管理IC开发工具 MAX5022 Eval Kit RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| MAX5023 | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:65V, Low-Quiescent-Current, High-Voltage Linear Regulators with レP Reset and Watchdog Timer |
| MAX5023_05 | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:65V, Low-Quiescent-Current, High-Voltage Linear Regulators with μP Reset and Watchdog Timer |
| MAX5023_ASA | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:65V, Low-Quiescent-Current, High-Voltage Linear Regulators with レP Reset and Watchdog Timer |
| MAX5023LASA | 功能描述:线性稳压器 - 标准 65V Low-Q w/uP Reset & Watchdog Timer RoHS:否 制造商:STMicroelectronics 输出类型: 极性: 输出电压:1.8 V 输出电流:150 mA 负载调节: 最大输入电压:5.5 V 线路调整率: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOT-323-5L |
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